1. Field of the Invention
The present invention relates to impact type crushers, and more particularly, to those which utilize centrifugal force to hurl the rocks to be crushed against the anvils.
2. Prior Art
Impact type crushers which utilize centrifugal force to hurl rocks to be crushed against anvils are generally known. For example, such devices are disclosed in the following U.S. Pat. Nos. 3,767,127; 3,652,023; 3,578,254; and 3,474,974.
The developers of these types of devices have been primarily concerned with increasing the useful life span of the apparatus, particularly those portions of the apparatus which come in contact with the rock such as the impeller assembly and the anvils. These portions of the devices are subject to wear due to impingement of the rocks on the impeller vanes and upper and lower wear plates while they are accelerating the rock, and the faces of the anvils which crush the rock. These portions of the devices have therefore been designed also to be easily removable and replaceable, since substantial wearing does occur.
A difficulty associated with such prior art devices is in the utilization of horizontally disposed upper and lower surfaces forming the top and bottom of the channels defined between the impeller vanes in the impeller assembly. The use of such horizontal surfaces results in a non-horizontal trajectory of rock as it is hurled from the channels. Instead the rock tends to fly upwardly and impinge on the upper portions of the anvils, causing uneven wear and significantly reducing the useful life of the anvils.
The landing area in the central region of the impeller where the rocks are initially deposited before they are thrown from the impeller has also been a problem in the past. If the landing area is flat, it has been discovered that the rocks tend to remain on the landing area sufficiently long to wear grooves in the surface of the landing area, thus affecting the outward movement of rocks as the wearing progresses. On the other hand, it has also been discovered that if the angle of the surface of the landing area relative to the horizontal is too great the rocks to be crushed proceed radially outwardly at too fast a rate so that they are not accelerated sufficiently in rotation by the landing cone to minimize damage to the inner apex portions and the working sides of the impeller vanes.
In conventional, centrifugal rock crushers the anvils are formed as single piece castings. This results in a relatively hard outer surface but in a relatively soft core. As a result, once the hardened outer surface is worn through, further wear occurs at a rapidly increasing rate and seriously increases the frequency with which the anvils must be replaced.